Automatic beacon range indicator



March 9, 1954 D. PERKINS 2,671,895

AUTOMATIC BEACON RANGE INDICATOR Filed Feb. 15, 1946 M 5 \Y 1/ M l8 l0 l2\ 4 2l SYNCHRO- GA DELAY BEACON N|ZER DEE/A}? I LINE T I i [22 TRANS- GATE STEP GATE MITTER GENERATOR GENERATOR 19x Y I REcEIvER I F I I I SWITCH SWITCH I A j l,

35 INTEGRATOR RELAY 28 I swlTcI-I I JUNCTION I I I CODE CQDER GATE 29 I COMPARATOR I 5&5; I I MOTOR TRANSMITTER PULSE GATE DELAY TRIGGER REcEIvER GATE POSITIVE STEP GATE NEGATIVE STEP GATE REPLY sIGNAL I INVENTOR.

GEORGE D. PERKINS ATTORNEY Patented Mar. 9, 1 954 ET FFICE AUTOMATIC BEACON INDICA'ELQ'R George D. Perkins, Salem, Mass assi'g'nor, by mesn'e assignments, to the United States of America as represented by the Secretary or the Navy Application February 15, 1946; Serial No. 647,957

19' Claims. (Cl. 3'3-=-6.5)

l 2 This invention relates to radio ranging devices In Fig. 1, unit it! is a synchronizer which and more particularly to such devices for auto triggers transmitter H and gate delay unit t2. matical ly' indicatingtherange to a selected sta- Transmitter it sends out pulses of electromagtion. neticenergy through antenna It at a predeter- An aircraft pilot often desires range informarained repetition rate. The radiation from antion with respect to aground station of known tenna which with its associated equipment location. A conventional method for providing is considered to be mounted in an aircraft, is such data involves the use of a challenging radar received by antenna ii of beacon unit l8, which set in the plane to trigger a transp'ondor beacon is aground station remote from the aircraft. on the ground. When triggered by a pulse from Each pulse of interrogating transmitter H is the radar transmitter, the transponder beacon therefore received by beacon l8 and triggers on sends back. a series of pulses which are coded in acomponent transmitter of beacon f8, sending time, the firstof these pulse signals appearing on back a reply pulse for each pulse of inthe radar indicator at the range of the beacon terrogation. However, after or seconds of and the other pulses in the series appearing at replying pulse for pulse, there is a gap in beacon longer ranges with spacings determined by the its transmission followed by a coded reply particular code used. Another type of transsequence of pulses constitutingaMorse code'letter pondor beaconrepliespulse'for'pulse to the radar identification of the beacon. This is a type of transmitter except for predetermined gaps in beacon in common use.

the replieswhich constitute a coding. system. The reply signals from beacon I8 are picked Here the: beacon signal appears on the radar by antenna t6 and applied to receiver l'9. indicator as a continuous signalatthe rangebe- Receiver It is normally blocked off. However, tween plane and beacon, except for the coding when synchronizer in fires transmitter H, it also gaps in the: signal. Both types of presentation pulses gate delay unit i2. Gate delay unit l2 require concentration and some degree of skill includes a potentiometer whose slider contact on the part of the operator to identify the proper controls the interval of delay between the pulse beacon as: wellas to read the range, and are received from synchronizer m and the output particularly impractical for use ina singleseate'r pulse from unit 12'. The output delayed pulse plane. from gate delay unit I2 triggers gate generator The present invention simplifies matters for no 29. By the term gate as used here and hereinthe: pilot by permitting him to turn a selector after in this specification is meant a voltage pulse switchto: aposition corresponding to the coding used for gating or otherwise activating a succeedof" the: particular beacon on which he wishes to ing'i circuit. The gate output of unit 29' sensitizes home. His apparatus'then automatically locks receiver 9 for a predetermined time set-by the on the beacon and giveshim: a visual indication :7. gate length. It will be noted that gate delay unit on a meter of the range to the desired beacon. it thus controls the interval between the firing objector this invention is to providean of transmitter H and the sensitizing of reelectronic automatic indicator of the range beceiver H 9;

tween anaircraft and a beacon. At the same time that the output pulse from Another object'is to provide an electronic au- 4i gate delay unit l2 triggers gate generator 20', tomatic indicator of the identity of a selected is pp d delay line 2| Which has a delay beacon. time of half the predetermined length of the Anoth'er'objectis'to provide an automatic range g te" ou' 'p l o u The pu pulse from indicator system to enable an: aircraft to track delay line 2! triggers step gate generator 22, achain-of beacon stationsfiom the takeofipoint producing two phase-opposed s' tep gates. The to it'sdestination; positive" step gate is applied to switch tube 26 These and other objects and features or this and the: negative step gate to switch tube- 21'. invention will become apparent upon considera- Positive-video pulses of reply signals from beacon tion' of" the following detailed description when E8 are" also supplied to switch tubes 26 and El takentogether with the accompanying drawby receiver is; The switch tubes 28 and 2 1 can ings, inwhich: beof several types and the switching action can: Fig. 1 isa blo'ck'di'a'gram of an automatic range be accomplished in various Ways. For purposes indicator; and of illustration, switch tubes 25 and 21 will be Fig. 2 illustrates the time relati'onsh'ipcf opconsidered to be thyratrons. The positive video emu-on of the units of Fig. 1 pulses from receiver as are applied to the thy ratron grids and the step gates from unit 22 are applied to the cathodes of the thyratrons. Thus, switch tube 26 will be conditioned to conduct in the time preceding the step in the middle of the gate. Switch tube 21 will be rendered nonconducting during the same time because the high voltage on its cathode will not permit the plate to cathode voltage to reach a firing potential. Similarly after the step occurs in the step gates from unit 22, switch tube 26 will be rendered non-conducting and switch tube 21 will be conditioned to conduct upon a positive trigger applied to its grid. Let gate delay unit I2 set the interval between a first interrogating pulse of transmitter II and the activating of receiver I9 such that the first reply signal received from beacon I8 occurs in the first half of the enabling gate generated by unit 20. Then switch tube 26 will be triggered by the first video reply pulse from receiver I9 and will conduct. The triggering of switch tube 26 closes a first relay in relay junction 23 which in turn closes a power supply circuit to gate delay sweep motor 29. Switch tube 26 stops conducting when the step in the positive step gate is reached and jumps the oathode potential to drop the plate to cathode voltage below the extinction potential. During the time switch tube 26 is conducting, motor 29 drives the slider arm of the potentiometer of gate delay unit I 2 so as to decrease the interval between the second firing of transmitter II and activating of receiver I9. This process has the effect of moving the step gate outputs from unit 22 relative to the second reply video pulse of beacon I8 from receiver I9 so that the step moves to coincide with the video pulse. In like fashion, if the reply signal received from beacon I8 occurs in the second half of the activating gate generated. by unit 20, switch tube 21 conducts, closing a second relay in relay junction 28 and causing motor 29 to run in reverse. In other words, switch tubes 26 and 21 generate error signals when the beacon reply signals are displaced from the center of the activating gate from unit 20, causing the controlled interval of gate delay unit I2 to be varied in order to place the reply signals in the center of the activating gate. In the absence of a reply signal during the period of activating of receiver I9, a relay in relay junction 28 is closed, causing motor 29 to operate and change the gate delay of unit I2 in what may be likened to a sweeping process in search for a signal. A point of equilibrium is reached when the step of the step gate outputs from unit 22 coincides with the video pulse from receiver I9. Then the position of the slider arm of the control potentiometer of gate delay unit I2 is proportional to the range between the interrogating transmitter I I and the ground beacon I8. A range meter 30 comprises a voltmeter, calibrated in range units, connected across the above-mentioned potentiometer.

By reference to Fig. 2 the time relationship between the trigger and gates of the units of Fig. 1 will be seen and the operation of this automatic range indicator more readily understood. Pulse 4!! represents the first output pulse of transmitter II coincident with that of synchronizer II. Trigger M is the first output pulse of gate delay unit I2 coming at a variable controlled interval after transmitter pulse 40. The output of gate generator 20 is receiver gate 42 and this starts coincident with trigger 4|. Step gate generator 22 produces positive step gate 43 and negative step 44 having a step coinciding with the center of gate 42 as shown by the dotted vertical line. The first beacon reply signal 45 is shown preceding the center of gate 42 and the step of step gates 43 and 44. Therefore switch tube 26 would fire causing gate delay sweep motor 29 to decrease the delay time of unit I2. The second pulse 46 of transmitter II is followed by trigger 41 of gate delay unit I2, the time between 46 and 41 being shorter than the time between and M. This has the effect of moving gates 48, 49 and 50 to the left with respect to the second beacon reply signal 5| which follows transmitter pulse 46 by substantially the same interval as reply signal followed interrogating pulse 40. Reply signal 5| is shown as coinciding with the center of receiver gate 48 in which case the equilibrium point referred to above is reached. As the range between interrogater and beacon changes and the beacon reply pulse tends to drift from the center of the receiver gate, gate delay sweep motor 29 will be energized and automatically vary the delay provided by unit I2 to keep the beacon reply signals centered in the receiver gate.

Thus the illustrative embodiment of this invention registers automatically the range between an aircraft and a ground beacon or between any station equipped with interrogating equipment and any station equipped with beacon equipment according to this invention. It will be readily apparent to those skilled in the art that the component units of this invention may have alternative forms. For instance, switch tubes 26 and 27 alternatively can take the form of coincidence amplifiers requiring simultaneous signals on control and screen grids for triggering. The step gate generator 22 as a one-shot or a driven multivibrator very simply provides phaseopposed step gates taken from the plates or cathodes respectively of both stages. Similarly units I2 and 20 could take the form of conventional multivibrators designed for the functions concerned.

In addition to providing range data to a beacon station, this invention provides for automatic selection of a desired beacon to which range information is sought. During the time in which beacon I8 is sending back a reply pulse for each pulse of transmitter I I, integrator switch unit 35 integrates each output video pulse from receiver I9 to maintain a voltage level above that required to keep a coder relay closed in relay junction 28. When the gap occurs in the pulse for pulse transmission of beacon I8 to be followed by the Morse code identification pulses, the voltage output from the integrating circuit of unit 35 decays and allows the coder relay to drop out. This sets coder 36 into operation to key a locally generated code corresponding to that of the beacon which the pilot desires to locate. A convenient form of coder is a motor driven disc properly segmented to key a desired Morse code signal. A selector switch incorporated in coder 36 permits selection of any one of a plurality of codes corresponding to a plurality of beacon stations. The coded pulse output of coder 36 is applied to code comparator 31 where it is compared to the coded pulse output of beacon I8 as received by receiver I9. One type of comparator would be a balanced push-pull amplifier having the received beacon signal applied to one stage and the locally generated code from coder 36 applied to the other stage. If the codes match, no output from comparator 31 results and the automatic range indicator of this invention stays locked on the particular beacon which is being tracked since it is the one being sought. If, however, the codes do not match, code comparator 31- operates the search: relay in relay junction 28, causing gate delay sweep motor 29 to operate gate delay unit 12 in search of another signal. The swept search continues until the correct beacon is received and its identity is further rechecked each time the Morse coded signal is received by receiver to.

Although there is shown and described only a certain specific embodiment oi this invention, the many modifications possible thereof will be readily apparent to those skilled in the art. Therefore, this invention is not to be limited except insofar as is necessitated by the prior art and the spirit of the appended claims.

What is claimed is:

I. automatic range indicator comprising, means for generating and transmitting a series of interrogating pulses or electromagnetic energy, beacon means responsive to said series of pulses for generating electromagnetic reply signals of a. predetermined sequence, means associated with said interrogating means for receiving said reply signals, voltage pulse gating means for activating said receiving means for a predetermined time at a controlled interval after each of said interrogating pulses, means for generating first and second phase-opposed step gating pulses each having a step coinciding with the center of said activating gating pulses, first and second switching means responsive to the combination of said reply signals and said first and second step gating pulses respectively for generating an error signal when any one of said reply signals is displaced from the center of said activating gating pulse, means, responsive to said error signal for varying said controlled interval to place said reply signals in the" center of said activating gating pulse, and means for measuring said controlled interval to indicate the range between said interrogating means and Said beacon.

2. An automatic, range indicator comprising, a syncroniizer, a transmitter triggered by said synchronizer for transmitting interrogatimz pulses,v of electromagnetic energy, an antenna for, radiating said interrogating pulses and receiving coded reply signals imin beacons responding to said interrogating ulses, a receiver for said reply signals, a voltage pulse. gate delay generator triggered by said synchronizer, said. gate delay generator including a potentiometer control element, a voltage pulse gate generator coupled tov said gate delay generator for activating said receiver, a. delay line for delaying the output of said gate delay generator, a voltage pulse step gate generato'r responsive to said delayed output for produping first and second phase-opposed voltage pulse step. gates, first. and second switch tubes responsive to the combined amplitudes of said reply signals and said first and second stepgates respectively for. producing an error signaloutput, first and second relays, responsive to said. error signal output, a voltage pulse gate delay sweep motor coupled to. said first and second relaysfor driving the slider arm oi said potentiometer of said gate delay generator, at voltmeter connected between saidslider arm and one end of said potentiometer for measuring the voltage correspending to the time delay between each of said interrogatmg pulses and said reply signals, an integrating circuit responsive to said coded beacon reply signals, a coder coupled to said G. integrating circuit for generating a selected code of pulses, and a code comparatorcoupled to said receiver, said coder and said gate delay sweep motor, whereby if said beacon reply signals not match the selected code said gate delay sweep motor varies the time interval between said interrogat-ing pulses and said activating of said re ceiver until the correct beacon is received and said voltmeter then registers the range: between said transmitter and said beacon.

3. Apparatus for continuously indicating therange to a beacon from an mterrogating means in a system of the type in which the interrogating means transmits a series of interrogating pulses and the beacon transmits a series of reply pulses inresponse thereto, said apparatus comprising, a receiver associated with said interrogating means for receiving said reply pulses, means for tic-ti vating said receiver for a predetermined period following a controllable interval after each of said interrogating pulses, means for generating first and second phase-opposed gating pulses having leading edges occurring in time coincidence with the mid-point of. said predetermined period, means responsive to the combination of said. reply pulses and said first and second gating pulses, respectively, for producing an error signal when any one of said reply pulses is displaced from the mid-pointof said period, means responsive to said error signal for varying said controllable interval to place said reply signals at the mid-point of said predetermined period, and means for measuring said. controllable interval to continuously indicate the range to said beacon.

d. An automatic range indicator comprising, means for transmitting a series. of interrogating pulses of electromagnetic energy, a remotebeacon responsive to said series of pulses for transmitting reply pulses of a predetermined sequence, means associated with said interrogating means for receiving said series of reply pulses, means for gencrating a first gating pulse for activating said: receiving means for a selected period. following a controllable interval after each of said interrogating pulses, means for generating second and third phase-opposed gating pulses having leading edges coinciding with the center of said first gating pulse, means responsive to the combination of said reply signals and said second and. third gating pulses, respectively, for generating an error signal when any one of said reply pulses is displaced from the center of: said first gating pulse, and means responsive to said: error signal for varying said, controllable interval to place said reply pulses in the center of said first gating pulse.

5; An. automatic range indicator comprising, means for transmitting av series of interrogating pulses of electromagnetic energy, a remote beacon responsive to said series of pulses for transmitting reply pu-lses of a predetermined sequence, means for receiving said series of reply pulses, means for generating a first gating pulse for ac-- tivating said receiving means for a predetermined period fol-lowing a controllable interval after each of said interrogating pulses, means including a delay line for generating second and third phaseopposed gating pulses having leading edges coiniciding. with the center of said first gating pulse, first and second switching means: responsive to the combination of said reply signal and said second and third gating pulses, respectively, for generating an error signal when any one of said replypulses is displacedfrom the center of said first gating pulse, means responsive to said error signal fcr'varying said controllable interval to place said reply pulses in the center of said first gating pulse, and means for indicating the duration of said controllable interval.

6. An automatic range indicator comprising, means for transmitting a series of interrogating pulses of energy, a remote beacon responsive to said series of pulses for transmitting reply pulses, means for receiving said reply pulses, means including a potentiometer control element for producing a first gating pulse for activating said receiving means during a predetermined period following a controllable interval after each of said interrogating pulses, means for generating second and third phase-opposed gating pulses having leading edges coinciding with the center of said first gating pulse, means responsive to the combined amplitudes of said reply signals and said second and third gating pulses, respectively, for producing an error signal when any one of said reply pulses is displaced from the center of said first gating pulse, and a motor coupled to said potentiometer control element and responsive to said error signal for varying said controllable interval to place said reply pulses in the center of said first gating pulse.

'7. An automatic range indicator for a beacon system comprising, means for transmitting a series of interrogating pulses, remote beacon responsive to said series of pulses for transmitting a series of reply pulses, a receiver for said reply pulses, means including a potentiometer control element for generating a first gating pulse having a predetermined duration and a leading edge controllably delayed in time from said interrogating pulses for actuating said receiver, means responsive to said first gating pulse for generating second and third phase-opposed gating pulses having leading edges delayed from the leading edge of said first gating pulse by an interval equal to one-half the duration of said first gating pulse, first and second switch tubes responsive to the combined amplitudes of said reply pulses and said second and third gating pulses, respectively, for producing an error signal when any one of said reply pulses is displaced from the center of said first gating pulse, a motor coupled to said potentiometer control element and responsive to said error signal for varying the delay between the leading edge of said first gating pulse and said interrogating pulses to place said reply pulses in the center of said first gating pulse, and means for measuring said controllable delay to indicate the range between said interrogating means and said beacon.

8. Apparatus for continuously indicating the range to a selected beacon from an interrogating transmitter in a system wherein the beacon transmits a coded reply signal in response to interrogating pulses, said apparatus comprising,

a receiver associated with said transmitter for receiving said reply signal, means including a potentiometer control element for producing a first gating pulse for activating said receiver for a predetermined period following a controllable interval after each or" said interrogating pulses, means including a delay line for generating second and third phase-opposed gating pulses, means responsive to the combined amplitudes of said reply signal and second and third gating pulses, respectively, for producing an error signal when any one of said reply signals is displaced from the center of said first gating pulse, a motor connected to said potentiometer control element and responsive to said error signal for controlling said interval to place said reply signals at the center of said first gating pulse, and a code comparator for comparing said reply signals with a selected code of signals, said code comparator being coupled to said motor to cause said motor to vary said interval until said reply signals match said selected code.

9. Apparatus for continuously indicating the range to a selected beacon from an interrogating transmitter in a system wherein the beacon transmits a coded reply signal in response to interrogating pulses, said apparatus comprising, a receiver associated with said transmitter for receiving said reply signal, means including a potentiometer control element for producing a first gating pulse for activating said receiver for a predetermined period following a controllable interval after each of said interrogating pulses, means including a delay line for generating second and third phase-opposed gating pulses, means responsive to the combined amplitudes of said reply signal and second and third gating pulses, respectively, for producing an error signal when any one of said reply signals is displaced from the center of said first gating pulse, a motor connected to said potentiometer control element and responsive to said error signal for controlling said interval to place said reply signals at the center of said first gating pulse, means for measuring said interval to continuously indicate the range to said beacon, means responsive to said reply signal for generating a selected code of pulses, and a code comparator coupled to said lastmentioned means, said motor and said receiver and being arranged whereby beacon reply signals which do not match the selected code cause said motor to vary said controllable interval until the selected beacon is received and said measuring means indicates the range of said selected beacon.

10. Apparatus for continuously indicating the range to a selected beacon from an interrogating transmitter in a system wherein the beacon transmits a coded reply signal in response to interrogating pulses, said apparatus comprising, a receiver associated with said transmitter for receiving said reply signal, means including a potentiometer control element for producing a first gating pulse for activating said receiver for a predetermined period following a controllable interval after each of said interrogating pulses, means including a delay line for generating second and third phase-opposed gating pulses, means responsive to the combined amplitudes of said reply signal and second and third gating pulses, respectively, for producing an error signal when any one of said reply signals is displaced from the center of said first gating pulse, a motor connected to said potentiometer control element and responsive to said error signal for controlling said interval to place said reply signals at the center of said first gating pulse, means coupled to said receiver and said motor and arranged whereby beacon reply signals which are of a different code than that from said selected beacon cause said motor to vary said interval until signals from said selected beacon are received and positioned at the center of said first gating pulse, and means coupled to said potentiometer for measuring said controllable interval, said interval being a measure of the range to said selected beacon.

GEORGE D. PERKINS.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Gunn Nov. 1, 1938 Hershberger July 9, 1946 Wolff et a1. July 9, 1946 Graham July 16, 1946 Seeley Aug. 6, 1946 Seeley Aug. 6, 1946 Rosa May 27, 1947 Norgaard Nov. 30, 1948 Number 10 Name Date Grieg Jan. 25, 1949 Joyner Mar. 24, 1949 Jacobsen Sept. 20, 1949 Oliver Oct. 4, 1949 Mozley Jan. 31, 1950 Barchok July 18, 1950 Deloraine Nov. 28, 1950 Barchok et a1. Feb. 6, 1951 Stearns Feb. 27, 1951 

